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Agressive increasing of lower bound. #3997

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Agressive increasing of lower bound. #3997

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10 changes: 8 additions & 2 deletions src/search.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -552,7 +552,7 @@ namespace {
Key posKey;
Move ttMove, move, excludedMove, bestMove;
Depth extension, newDepth;
Value bestValue, value, ttValue, eval, maxValue, probCutBeta;
Value bestValue, value, ttValue, eval, maxValue, probCutBeta, initialAlpha;
bool givesCheck, improving, didLMR, priorCapture;
bool capture, doFullDepthSearch, moveCountPruning, ttCapture;
Piece movedPiece;
Expand All @@ -567,6 +567,7 @@ namespace {
moveCount = captureCount = quietCount = ss->moveCount = 0;
bestValue = -VALUE_INFINITE;
maxValue = VALUE_INFINITE;
initialAlpha = alpha;

// Check for the available remaining time
if (thisThread == Threads.main())
Expand Down Expand Up @@ -1296,7 +1297,12 @@ namespace {
update_pv(ss->pv, move, (ss+1)->pv);

if (PvNode && value < beta) // Update alpha! Always alpha < beta
alpha = value;
{
if (beta < VALUE_INFINITE && initialAlpha > -VALUE_INFINITE)
alpha = std::max(value, (beta - 1 + initialAlpha) / 2);
else
alpha = value;
}
else
{
assert(value >= beta); // Fail high
Expand Down